Separation of meta and para-cresol

ABSTRACT

A process is defined for the separation of para-cresol from admixture with meta-cresol by the selective condensation of metacresol with isobutyraldehyde using a catalyst comprising an aqueous solution of a hydrogen halide.

Jones et al. ..260/621 B United States Patent 1m 1111 3,725,485 Martini 1 1 Apr. 3, 1973 54] SEPARATION OF META AND PARA- 1,214,414 1 1917 Berend ..260/62l B CRESOL FOREIGN PATENTS OR APPLICATIONS [75] Inventor: Joseph C. Martini, Houston, Tex.

3,713,973 9/1962 Japan .260/62l B [73] Assignee: Gulf Research & Development Com- P y Pittsburgh, Primary Examiner-Howard T. Mars [221' Filed: Nov. 12, 1970 Attorney-Meyer Neishloss, Deane E. Keith and Richard C. Gaffney [21] Appl. No.: 89,123

Related U.S. Application Data [57] ABSTRACT [60] Division of Ser No 809 947 March 24 1969 Pat A process is defined for the separation of para-cresol 3,598 842 is aconfinuation in pan from admixture with meta-cresol by the selective con- No 731,251, 22, 1963 abandoned densation of meta-cresol with isobutyraldehyde using r a catalyst comprising an aqueous solution of a 521 0.8. CI. ..260/621 A, 260/346.2, 260/838 hydrogen [51'] Int. Cl. ..C07l 39/02 [58] Field of Search ..260/621 A, 621 B [56] References Cited 6 Claims, No Drawings SEPARATION OF META AND PARA-CRESOL of para-cresol from admixture with meta-cresol by selective condensation of the meta-cresol using isobutyraldehyde and an aqueous hydrogen halide catalyst. The reaction of aldehydes, such as formaldehyde,

with phenol and other phenolic compounds to form phenolic resins is well known in the art. lt has now been found that certain aldehydes, such as isobutyraldehyde, are unique in their reaction with certain phenolic com pounds having a hydrogen atom directly attached to the ring carbon atom adjacent the phenolic hydroxyl group to form cyclic ethers.

In accordance with the invention, it has been found that meta and para-cresol can be effectively separated from admixture with each other by the selective condensation of meta-cresol with isobutyraldehyde in the contact presence of an aqueous solution of -a hydrogen halide catalyst under condensation conditions.

It has been found that meta-cresol will selectively condense with isobutyraldehyde in the presence of para-cresol so long as the catalyst employed is an aqueous solution of a hydrogen halide. By a hydrogen halide is meant HF, HCl, HBr or HI. The preferred hydrogen halide is HCl.

The amount of the acid catalyst to employ in the subject reaction, based on the anhydrous hydrogen halide, is generally quite small, being'on the order of 0.1 percent by weight to percent by weight of the metacresol with preferred concentrations of the acid (based on anhydrous hydrogen halide) being between 0.3 and 7.0 percent by weight of the metacresol. It is preferred to employ the aqueous hydrogen halide catalysts in as high a concentration of the hydrogen halide component as possible in order to minimize the water content in the reaction zone. When hydrochloric acid is employed, for example, the commercial 37 percent solution is satisfactory. I

The molar ratio of the isobutyraldehyde to the phenolic reactant (meta-cresol) can suitably be from 0.8:] to 2.221. The preferred molar ratios are from 1.8:] to 2.221.

An inert solvent can be used to aid in contacting the reactants, to maintain any resin formed (some byproduct phenolic resin can form) in solution, to aid in maintaining the reaction temperature and to aid in the removal of the water of reaction if desired. The preferred solvents are the organic solvents, toluene and xylene. It is preferred that the solvent be such that the reactants are maintained in a homogeneous phase.

The reaction temperature can suitably be from to 200 C. The preferred reaction temperatures are from to 150C. Temperatures lower than 80 C. are not suitable since the reaction rate is undesirably slow. Temperatures above 200 C. are undesirable since they tend to promote larger amounts of the resinous byproduct. A

The reaction pressure is not critical and can suitably be from atmospheric or below to 1,000 psig or higher. Atmospheric pressure is, of course, preferred for economic reasons. The pressure should be sufficient to maintain the aldehyde and cresol reactants in the liquid phase.

The reaction time is not critical. Suitable reaction times can be as low as several minutes to 20 hours or more. Preferred reaction times arebetween 0.5 andlO hours, with the most preferred reaction times between 2 and 8 hours. The reaction time is, of course, a function of the reaction temperature, catalyst, catalyst concentration and reactivity of the aldehyde and phenolic charge stocks. Anyone with ordinary skill in the art can determine from a few simple experiments an optimum reaction time for the particular set of conditions, type of reactants and catalysts he employs.

There is nothing critical about the manner of contacting the reactants. The aldehyde and the mixture of meta and para-cresol can suitably be added separately or together to a reaction vessel and the acid catalyst and solvent, if employed, added before, after or during the addition of the reactants. Preferably, the acidcatalyst is added to a mixture of the aldehyde-phenolic reactants containing a solvent, if employed. The reaction mixture can then be heated to the desired reaction temperature by any suitable means. The reactants can also, of course, be preheated separately or together before entering the reaction zone, this latter method being more suitable to a continuous type of operation. After a suitable reaction time the by-products are recovered by any suitable means such as by distillation or by caustic washing followed by distillation.

The invention will be further described with reference to the following experimental work.

A series of runs was made to recover substantially pure para-cresol from admixture with meta-cresol by selective condensation of the meta-cresol with isobutyraldehyde using an aqueous solution of HCl (37 percent) as the catalyst. The molar ratio of the isobutyraldehyde to the meta-cresol varied from 0.8:1 to 2:1. The results of these runs (Examples l-5). are given in the table below.

Referring to the table, it can be seen that the metacresol selectively condenses with the isobutyraldehyde, especially as the molar ratio of the aldehyde to metac resol approaches 2:1. In Example 4, where the molar ratio of isobutyraldehyde to meta-cresol was 2:1, the purity of the para-cresol recovered was 100 percent.

EXAMPLE 6 In the run for this example, 216 grams (2 moles) of a mixture of meta and para-cresol, containing 50 weight percent meta-cresol, was reacted with two moles of isobutyraldehyde at a temperature between and 98 C. for 5 hours using 1.5 percent by weight of the cresol of sulfuric acid having an H SO content of 98 percent. Water was not removed during the reaction. The conversion of the cresols was 65 percent, and theyield and efficiency to the formation of a mixture of 2,2,6- trimethyl coumaran and 2,2,5-trimethyl coumaran was 49.5 and 76 percent respectively. The recovered unreacted cresols contained 26.8 percent by weight metacresol. 69.2 grams of a resinous byproduct having a molecular weight of 565 was obtained. This run is summarized on the table below.

A comparison of Examples and 6 shows that HCl is unique in its ability to selectively condense the metacresol with the isobutyraldehyde. In Example 6, the molar ratio of isobutyraldehyde to meta-cresol was 2:1 but the recovered cresols contained 26.8 percent meta and only 73.2 percent para-cresol compared to 100 percent para-cresol using HCl (Example 5). The poor results of Example 6 were obtained because sulfuric acid was used as the catalyst rather. than an aqueous hydrogen halide.

TABLE Example No.

l 2 3 4 5 6 Charge Stock Phenol mixture of m and p-cresol m-cresol 60 60 60 60 50 50 Total Grams 180 180 180 900 216 216 Total Moles 1.67 1.67 1.67 8.35 2 2 Aldehyde lsobutyraldehyde Mole Ratio, Aldehyde to m-cresol 0.8:1 0.9:1 1:1 1.221 2:] 2:1 Reaction Conditions Temperature, C.

98-107 94-120 97-104 100-113 89-103 95-98 Time, Hours 3 3 5 5 3 5 Pressure Atmospheric Catalyst Wt.% Anhydrous l-lCl 0.73 0.73 2.2 0.8 2 Wt.% Sulfuric Acid (98% H2804) 1 5 Results Wt.% Conversion of Cresols 61.5 68.5 66.7 69 69 65 Yield of Coumaran 25.4 15.1 11.7 8.5 49.5 Efficiency to Coumarans 22.8 37.2 22.6 17.3 12.3 76 Resin Wt., Grams 126.6 133.9 165.1 936.8 251 69.2 Molecular Weight 360 390 415 440 525 565 m-Cresol Recovered Based on Charged 23.2 17.3 12.3 8.9 0 -Cresol Recovered as'ed on Charged 54.2 52 1 54.3 44.4 62.6 Purity of p-Cresol Recovered Based on total mixture of m and p-cresol Added as a 37% aqueous solution EXAMPLE 7 Example 4 was repeated except formaldehyde was used in place of isobutyraldehyde, the reaction time was increased to 5 hours, and 1.5 percent by weight of the cresols of anhydrous HCl added as a 37 percent aqueous HCl solution was employed as the catalyst. Substantially all of the meta and para-cresol reacted to form resin, for only 0.9 percent by weight para-cresol was recovered. 252.7 grams of resin were recovered.

EXAMPLE 8 Example 7 was repeated except n-butyraldehyde was used in place of the formaldehyde. Substantially the same results were obtained.

A comparison of Examples 4, 7 and 8 shows the importance of employing an aldehyde as defined herein or the successful recovery of a substantially pure paracresol from admixture with meta-cresol.

Resort may be had to such variations and modifications as fall. within the spirit of the invention and the scope of the appended claims.

I claim:

1. A process for the selective condensation of metacresol from an admixture consisting essentially of metacresol and para-cresol which comprises contacting said admixture with isobutyraldehyde at a temperature from to 200 C in the contact presence of an aqueous solution of a hydrogen halide catalyst.

2. A process according to claim 1 wherein the hydrogen halide is hydrogen chloride.

3. A process according to claim 1 wherein the molar ratio of the isobutyraldehyde to the meta-cresol is from 1.8:1 to 22:1.

4. A process which comprises contacting a mixture consisting essentially of metaand para-cresol with isobutyraldehyde in the contact presence of an aqueous solution of a hydrogen halide catalyst at a temperature from 80 to 200 C and wherein the molar ratio of the halide to the meta-cresol is from about 1.8:1 to 2.211 and thereafter recovering a substantially pure paracresol.

5. A process according to .claim 4 wherein the hydrogen halide is hydrogen chloride.

6. A process according to claim 5 wherein the aqueous hydrogen halide contains about 37 weight percent I-lCl. 

2. A process according to claim 1 wherein the hydrogen halide is hydrogen chloride.
 3. A process according to claim 1 wherein the molar ratio of the isobutyraldehyde to the meta-cresol is from 1.8:1 to 2.2:1.
 4. A process which comprises contacting a mixture consisting essentially of meta- and para-cresol with isobutyraldehyde in the contact presence of an aqueous solution of a hydrogen haLide catalyst at a temperature from 80* to 200* C and wherein the molar ratio of the halide to the meta-cresol is from about 1.8:1 to 2.2:1 and thereafter recovering a substantially pure para-cresol.
 5. A process according to claim 4 wherein the hydrogen halide is hydrogen chloride.
 6. A process according to claim 5 wherein the aqueous hydrogen halide contains about 37 weight percent HCl. 